net: dsa: ocelot: build felix.c into a dedicated kernel module

The build system currently complains:

scripts/Makefile.build:252: drivers/net/dsa/ocelot/Makefile:
felix.o is added to multiple modules: mscc_felix mscc_seville

Since felix.c holds the DSA glue layer, create a mscc_felix_dsa_lib.ko.
This is similar to how mscc_ocelot_switch_lib.ko holds a library for
configuring the hardware.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Acked-by: Colin Foster <colin.foster@in-advantage.com>
Link: https://lore.kernel.org/r/20230125145716.271355-1-vladimir.oltean@nxp.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/dsa/ocelot/Kconfig

 # SPDX-License-Identifier: GPL-2.0-only
+config NET_DSA_MSCC_FELIX_DSA_LIB
+	tristate
+	help
+	  This is an umbrella module for all network switches that are
+	  register-compatible with Ocelot and that perform I/O to their host
+	  CPU through an NPI (Node Processor Interface) Ethernet port.
+	  Its name comes from the first hardware chip to make use of it
+	  (VSC9959), code named Felix.
+
 config NET_DSA_MSCC_FELIX
 	tristate "Ocelot / Felix Ethernet switch support"
 	depends on NET_DSA && PCI
@@ -8,6 +17,7 @@ config NET_DSA_MSCC_FELIX
 	depends on PTP_1588_CLOCK_OPTIONAL
 	depends on NET_SCH_TAPRIO || NET_SCH_TAPRIO=n
 	select MSCC_OCELOT_SWITCH_LIB
+	select NET_DSA_MSCC_FELIX_DSA_LIB
 	select NET_DSA_TAG_OCELOT_8021Q
 	select NET_DSA_TAG_OCELOT
 	select FSL_ENETC_MDIO
@@ -24,6 +34,7 @@ config NET_DSA_MSCC_SEVILLE
 	depends on PTP_1588_CLOCK_OPTIONAL
 	select MDIO_MSCC_MIIM
 	select MSCC_OCELOT_SWITCH_LIB
+	select NET_DSA_MSCC_FELIX_DSA_LIB
 	select NET_DSA_TAG_OCELOT_8021Q
 	select NET_DSA_TAG_OCELOT
 	select PCS_LYNX

drivers/net/dsa/ocelot/Makefile

 # SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_NET_DSA_MSCC_FELIX_DSA_LIB) += mscc_felix_dsa_lib.o
 obj-$(CONFIG_NET_DSA_MSCC_FELIX) += mscc_felix.o
 obj-$(CONFIG_NET_DSA_MSCC_SEVILLE) += mscc_seville.o
 
-mscc_felix-objs := \
-	felix.o \
-	felix_vsc9959.o
-
-mscc_seville-objs := \
-	felix.o \
-	seville_vsc9953.o
+mscc_felix_dsa_lib-objs := felix.o
+mscc_felix-objs := felix_vsc9959.o
+mscc_seville-objs := seville_vsc9953.o

drivers/net/dsa/ocelot/felix.c

@@ -2131,6 +2131,7 @@ const struct dsa_switch_ops felix_switch_ops = {
 	.port_set_host_flood		= felix_port_set_host_flood,
 	.port_change_master		= felix_port_change_master,
 };
+EXPORT_SYMBOL_GPL(felix_switch_ops);
 
 struct net_device *felix_port_to_netdev(struct ocelot *ocelot, int port)
 {
@@ -2142,6 +2143,7 @@ struct net_device *felix_port_to_netdev(struct ocelot *ocelot, int port)
 
 	return dsa_to_port(ds, port)->slave;
 }
+EXPORT_SYMBOL_GPL(felix_port_to_netdev);
 
 int felix_netdev_to_port(struct net_device *dev)
 {
@@ -2153,3 +2155,7 @@ int felix_netdev_to_port(struct net_device *dev)
 
 	return dp->index;
 }
+EXPORT_SYMBOL_GPL(felix_netdev_to_port);
+
+MODULE_DESCRIPTION("Felix DSA library");
+MODULE_LICENSE("GPL");